[BUG] Retry handling fails in some Bedrock throttling cases

[steffeng]

Checks

• I have updated to the lastest minor and patch version of Strands
• I have checked the documentation and this is not expected behavior
• I have searched ./issues and there are no duplicates of my issue

Strands Version

1.8.0

Python Version

3.13.7

Operating System

MacOS

Installation Method

pip

Steps to Reproduce

Call agent with Bedrock model (see model id below) often enough during busy hours of Bedrock so that an error is issued like this (mind the spelling of throttlingException):

botocore.exceptions.EventStreamError: An error occurred (throttlingException) when calling the ConverseStream operation: Too many requests, please wait before trying again. You have sent too many requests. Wait before trying again.
└ Bedrock region: us-east-1
└ Model id: us.anthropic.claude-3-7-sonnet-20250219-v1:0

Expected Behavior

Retry is handled by the agent in the same way as it currently handles the same error code with uppercase T (ThrottlingException).

Actual Behavior

Error is raised without retry.

Additional Context

I raised a ticket to Bedrock team as well, but no plan to fix, yet.

Possible Solution

If the error code is present, do lower() before comparison to throttlingexception.

Related Issues

No response

[vickipedia]

I had been hitting these consistently too. I did locally tamper the files to set .lower(), but those did not help. I had to configure Bedrock session to increase retries and max attempts. I had to set the mode to adaptive and increase the total_max_attempts count.

from botocore.config import Config


_client_config = Config(
    region_name = 'us-west-2',
    signature_version = 'v4',
    connect_timeout=120,
    read_timeout=120,
    retries = {
        'total_max_attempts': 99,
        'mode': 'adaptive'
    }
)

bedrock_model = BedrockModel(
    model_id=model_name,
    region_name =region,
    boto_client_config=_client_config

_agent = Agent(name="agent_name", system_prompt=system_prompts["agent_prompt"], 
                            model=bedrock_model, 
                            tools=agent_tools)

After this, I see a drastic drop in ThrottlingExceptions.

[steffeng]

Thanks @vickipedia! Yes, retries are handled on multiple levels and changing the AWS SDK retry config is yet another effective tweak.

This ticket is about cleaning up the strands-owned retry. Once the Exception is interpreted correctly as a throttling, the provider agnostic retry behavior is done. They requested to make this configurable in #283.

[mehtarac]

Fix merged. Closing.